However a new video card and in this case more than two and worse not even the same model makes me write to talk to it's designer and ask them to sort it out.

The RAM issue is usually a sign of too many sticks. That's a deep discussion about many areas but as you add more sticks the timing usually has to be slowed to allow for more chips on the bus. For blood thirsty gamers I like to see pairs of RAM and just one pair to maximum payoff without having to discuss why more chips = pain.

The X-Fi is both loved and hated. I'm sure you know why. Driver madness?
Bob